Portable ultrasound system with efficient shutdown and startup

ABSTRACT

An ultrasound system is described which can be turned off quickly and restarted to be ready for scanning in a matter of seconds. This is accomplished by allowing a processor and/or memory within the system to remain active even when the system is “turned off.” When the system is turned off the state of the system is minimally preserved in either volatile or nonvolatile memory so that the system can quickly restart without having to sequence through an entire bootup procedure.

This application claims the benefit of Provisional U.S. patentapplication Ser. No. 60/232,450, filed Sep. 13, 2000.

This invention relates to ultrasonic diagnostic imaging systems and, inparticular, to portable ultrasound systems which power-up rapidly to anoperating condition.

In today's efficiently run hospitals, the portability of an ultrasoundsystem enables the system to be used in more than one lab or department.An ultrasound system can be used in radiology for most of the time andwheeled into the obstetrics department or delivery room when needed foran obstetrical exam, for instance. Portability also enables anultrasound system to be used at the patient's bedside so that, insteadof moving a patient to the ultrasound lab, the ultrasound system ismoved to the patient, which is important in diagnosing many criticallyill patients. Frequently, medical emergencies will necessitate that theultrasound system be moved quickly and the examination commenced at onceat the new location. An impediment to such speed and convenience is thenecessity to turn off the conventional ultrasound system through atime-consuming shutdown sequence before it can be unplugged and moved.This delay is repeated at the new location when it is necessary to powerup the ultrasound system through a complex and time-consuming boot-upprocedure. Accordingly it would be desirable to avoid thesetime-consuming steps so that the ultrasound system can be relocatedimmediately and be ready to scan instantly at the new location.

In accordance with the principles of the present invention, anultrasonic diagnostic imaging system is described which can be turnedoff quickly and restarted and be ready for scanning in a matter ofseconds. This is accomplished by allowing a processor and/or memorywithin the system to remain active even when the system is “turned off.”When the system is turned off the state of the system is minimallypreserved in either volatile or nonvolatile memory so that the systemcan restart without having to sequence through an entire bootupprocedure. In a preferred embodiment the processor has a battery backup,enabling the processor to remain active even when the ultrasound systemis unplugged and being moved. When the ultrasound system arrives at itsdestination, diagnosis can begin at once.

In the drawings:

FIG. 1 illustrates in block diagram form an ultrasonic diagnosticimaging system constructed in accordance with the principles of thepresent invention;

FIG. 1a illustrates a method for initializing the ultrasound system ofFIG. 1;

FIGS. 2a-2 d illustrate different methods for efficiently turning off anultrasound system so that it can be restarted quickly;

FIGS. 3a-3 d illustrate different methods for rapidly restarting anultrasound system;

FIG. 4 illustrates a method by which an inactive ultrasound system canrespond to a remote inquiry;

FIG. 5 illustrates a method by which an inactive ultrasound systemautomatically prepares for scanning at a predetermined time; and

FIG. 6 illustrates a method by which an ultrasound system assumes astate of lower power consumption during periods of inactivity.

Referring first to FIG. 1, an ultrasonic diagnostic imaging system 10constructed in accordance with the principles of the present inventionis shown in block diagram form. The components of a typical ultrasoundsystem are shown at the top of the drawing, including a scanhead ortransducer 12, an image display 16, and the ultrasound signal path 14which connects the transducer and the display. The ultrasound signalpath will typically include a beamformer which controls the transmissionof ultrasonic waves by the transducer 12 and forms received echo signalsinto steered and focused beams, a signal processor which processescoherent echo signals in the desired mode of display, e.g., B mode,Doppler mode, harmonic or fundamental mode, and an image processor whichproduces image signals of the desired format from the processed echosignals, such as a 2D or 3D image or spectral Doppler display. Theultrasound signal path is controlled in a coordinated manner by a systemcontroller which responds to user commands and dictates the overallscheme of functionality of the ultrasound signal path. For instance, thesystem operator may enter a command on the user control panel 20 torequest two dimensional colorflow imaging using a certain scanhead. Thesystem controller would respond to this command by conditioning thebeamformer to operate and control the desired scanhead, initializing thesignal processor to Doppler process the received echo signals, andsetting up the image processor to produce a grayscale B mode image withflow shown as a color overlay.

The source of energy for a cart-borne or tabletop ultrasound system isgenerally a.c. line voltage accessed by a plug 40. The a.c. power isfiltered and rectified by an a.c. line conditioner 42, which produces aDC supply voltage such as 48 volts. This voltage is supplied to a signalpath power supply 18, which supplies power to the scanhead 12 andultrasound signal path 14. The a.c. line conditioner provides two otherfunctions, which are to sense and respond to different a.c. powersources and to provide power factor correction which matches current andvoltage phases to prevent instantaneous current spikes during cycles ofthe a.c. power. The a.c. line conditioner will sense whether the plug 40is connected to 110 volt, 60 Hz power or 220 volt 50 Hz power, forinstance, and will respond to configure the line conditioner to producethe required 48 VDC from either a.c. source. Power factor correctionwill cause the ultrasound system to use power more efficiently byappearing as a more resistive rather than reactive load to the a.c.power system. The power supply 18 is a DC to DC converter, whichsupplies a number of DC voltages for different components and modules ofthe ultrasound system. For instance, a high voltage is supplied as adrive voltage for the ultrasonic transducer, and lower level voltagesare supplied to the digital processing circuitry of the system. Thesignal path power supply 18 is generally capable of providing 1000 wattsor more of power to a cart-borne ultrasound system.

In accordance with the principles of the present invention a CPU board30 is coupled to the ultrasound signal path 14 which controls thepowering up and powering down of the ultrasound signal path. Thefunctions of the CPU board discussed below may, in a particularembodiment, be integrated into the system controller of the ultrasoundsignal path and be performed there. In FIG. 1 a separate CPU board isshown for ease of illustration and understanding. The CPU board 30 maycomprise an off-the-shelf motherboard such as an ATX form factormotherboard with a system core chipset and basic input/output (BIOS)software. BIOS is code that runs from some sort of non-volatile memorysuch as a PROM or flash storage device and stays resident on the CPUboard. The BIOS software boots the CPU from a cold power-up and launchesthe operating system. The BIOS software performs such functions aschecking basic hardware operability and hardware resources available.Vendors of BIOS software include Phoenix, Award, and AmericanMegatrends. The CPU board includes a CPU processor 31 (sometimesreferred to herein as the CPU) which may be a microprocessor such as themicroprocessors available from Intel, Advanced Micro Devices, orMotorola, or a processor of more limited capability such as a reducedinstruction set (RISC) processor. The CPU board includes a random accessmemory (RAM) 33 which enables the CPU to run an operating systemsoftware program (OS) resident on nonvolatile disk storage 34. The OS isoperated to control various operating aspects of the ultrasound signalpath 14, display 16 and peripheral devices connected to the ultrasoundsystem such as printers and recorders, as described below. The OS refersto the platform software that tends to housekeeping functions andprovides an interface to launch application software. Operating systemsoftware includes DOS, Windows95-2000, Windows CE and NT, Solaris, andOS2. Any software that is not an OS and performs a given task isreferred to as application software. Examples of application softwareincludes word processor software, spreadsheet software, communication oranalysis software, and the custom software that runs an ultrasoundmachine. In the illustrated embodiment the CPU board is coupled to theultrasound signal path 14 by way of a control interface shown as controlmodule 15 of the ultrasound signal path 14. When the functionality ofthe CPU board is integrated into the ultrasound signal path, the needfor this interface may be partially or wholly eliminated.

The CPU board may be powered by the signal path power supply 18,however, in the illustrated embodiment the CPU board 30 is powered byits own CPU power supply 32. The CPU power supply has a lower capacitythan that of the power supply 18, and may for instance be a 250 wattpower supply. The CPU power supply 32, like the power supply 18, is a DCto DC converter which converts the voltage level supplied by the a.c.line conditioner to the DC voltages required by the CPU board 30 and,preferably, also the disk storage 34. The CPU power supply is coupled tothe a.c. line conditioner and is energized in the same manner as thepower supply 18.

In accordance with another aspect of the present invention, theultrasound system includes an optional battery 50 which provides abackup source of power to the signal path power supply 18 and the CPUpower supply 32. The battery is charged by a battery charger 52 coupledto the a.c. line conditioner 42 so that the battery can be fully chargedwhenever the plug 40 is connected to a source of a.c. line voltage. Thebattery 50 is also coupled to the drive motors of articulation devices,when present, by which movable parts of the ultrasound system such asthe display 16 and control panel 20 can be raised, lowered, and tiltedfor the convenience of the operator. This enables the ultrasoundsystem's articulated components to be moved and adjusted even when thesystem is not plugged into a wall outlet.

The ultrasound system has connections for a network and/or modem bywhich diagnostic information obtained by use of the ultrasound systemcan be remotely stored or shared with others. The network and modemconnections also enable information from remote sources to be providedto the ultrasound system, such as electronic mail and reference imagelibraries as described in U.S. Pat. Nos. 5,897,498 and 5,938,607. In theembodiment shown in FIG. 1 these connections are made from the CPU board30, although in a particular embodiment they may also be made from theultrasound signal path 14.

When a conventional ultrasound system is turned on, it must initializeall of its functionality from a cold start, which can take many minutesto accomplish. Likewise, when the system is turned off, the ultrasoundsystem goes through a lengthy process to power down its various modulesand subsystems in an orderly but time consuming sequence. In anembodiment of the present invention, the CPU board is rarely, if ever,completely powered down. The CPU board controls the other components andsubsystems of the ultrasound system to be in various suspended states orentirely powered down, and may even itself go into a suspend or lowpower state, but is selectively available to be restored and to restorethe rest of the ultrasound system to full operation in a short or almostinstantaneous period of time.

In concept, the CPU board 30 and its OS and associated software act as acentral processor with the other elements of the ultrasound system,including the ultrasound signal path 14, in essence viewed as peripheraldevices to this central processor. The CPU board OS and, if desired,application software control the states of operation of these peripheraldevices, within the constraints dictated by the user, so that the entiresystem is run efficiently and effectively. This can entail directingother elements of the ultrasound system to be in a high state ofreadiness, or to be in various suspend states with different timeperiods to return to full operation and different levels of powerconsumption, or to be partially or completely powered down. Not onlydoes the CPU board OS control other elements of the system in this way;in a preferred embodiment it can impose these same controls on itself,even to a state in which the entire system is in a suspend state whereit is consuming only 5-10 watts or less of power and can thus bemaintained by battery power for a substantial period of time.

Several examples will illustrate the degrees of control which arepossible. If the OS detects a lengthy period of inactivity by theultrasound system, it may progressively power down or suspend operationof certain system components. The display for instance, might first beset to standby, then later powered down completely. Similar action mightbe taken with peripheral devices such as printers and recorders. Theperiods of inactivity after which these actions are automaticallyperformed can be set by the system operator. Selected elements and evenmajor portions of the ultrasound system which take little or virtuallyno time to reactivate can be powered down even for short periods of timesuch as a few seconds. For instance, when the operator freezes an imageon the display screen, major portions of the ultrasound signal path canbe placed in a low power suspend state until realtime scanning isresumed. This suspend state would be unnoticed by the operator, to whomthe system would always appear fully active. Such a suspend state mightonly last for a period of seconds, but the accumulation of such periodsover time can result in a significant reduction in power consumption andcomponent heat exposure and dissipation. Other elements of the systemmight always be maintained in a high degree of readiness, such as anetwork connection or modem, which would thus respond to queries at anytime of the day or night.

The ultrasound signal path may be set to different inactive state levelsfrom which it can return to full operation in a timeframe desired by thesystem operator. For instance, processors in the ultrasound signal pathcan be set to an idle state in which peripheral devices controlled oraccessed by the processors including the nonvolatile disk drivesservicing the processors are powered down. The processors and theirvolatile memory (RAM) continue to operate normally so that fulloperation can be restored almost immediately. In a lower inactive state,in addition to powering down the peripheral devices, the clock rate ofthe processors is reduced to a lower rate during inactive periods. Theprocessors continue to be energized, as does the volatile memory used bythe processors, which enables their resumption to full operability infractions of a second. In an even lower inactive state the processorsthemselves are powered down, and the context, or variable data, of theprocessors such as register values, stacks and index values of theprocessors are stored in RAM, which remains energized. When power isrestored to the processors a pointer restores the context of theprocessor to its state prior to shutdown, and full operability resumesfairly rapidly. In yet an even lower inactive state, the processorcontext is stored in RAM, and the RAM data is stored in nonvolatile(disk or semiconductor, e.g., flash) storage. The nonvolatile storage,RAM and processor are then shut down. When operation is resumed the RAMdata is retrieved from the nonvolatile storage, the context of theprocessor restored, and operation resumes from the point at which it wasinterrupted. In a machine as complex as an ultrasound system, differentprocessors may have different inactive state levels, chosen as afunction of the roles played by the various processors and the speedwith which the operator wants the system to return to full operation. Ifthe operator wants the system to return to full operation in fractionsof a second, for instance, the CPU board OS may set the lowest inactivestate for key processors to be that in which processor clock speed isreduced, but the processors and their volatile memory continue to beenergized. If a longer time to resume operation is acceptable, a lowerinactive state would be used. The sizes of data blocks used by thesystem is also a consideration. If large blocks of data are needed toconfigure the beamformer for scanhead operation and the time needed torestore the beamformer data from disk is unacceptable, the OS can causethe RAM memory of the beamformer in which the data is stored to becontinuously energized, obviating to restore the data from disk.

The following drawings illustrate flowcharts for operating an ultrasoundsystem in accordance with some of the foregoing considerations andoptions. These embodiments describe implementations of the presentinvention by an OS for ease of illustration; however, it will beappreciated that in a constructed embodiment the invention may beimplemented in whole or in part by the OS, application software, BIOSsoftware, or a combination thereof. The present invention can also beimplemented in hardware such as by FPGA (field programmable gate array)control in lieu of OS control. As used herein the term OS refers to anyof these approaches. FIG. 1a illustrates the flowchart of a process forinitializing a default operating state for the ultrasound system. Thedefault operating state is typically one which an operator uses mostoften. If the ultrasound system operator is an obstetrician, forinstance, the default operating state may be an obstetrical exam with aparticular curved array scanhead. If the ultrasound system operator is acardiologist, the default operating state may be a cardiac echo examwith a particular phased array scanhead. The default operating statewould typically be initialized the first time the operator uses theultrasound system, although it can be set or altered at a later point intime. In the process illustrated in FIG. 1a the ultrasound system isturned on (101) and the CPU board and its OS boot up (102). The OS inturn causes the ultrasound signal path to boot up (103). When theultrasound signal path is fully operational its functionality is tested(104) to verify that the system is fully functional, a step which may beselectively bypassed by the operator. The operator then uses the userinterface to select the default exam type (105). If the operator is anobstetrician, for example, an obstetrical exam may be selected. Theoperator also selects the scanhead to be used for the preferred exam(106). When all of the necessary parameters of the default operatingstate have been selected by the operator, the ultrasound system,preferably the OS, creates a file which defines the default operatingstate, referred to herein as the “DQuickStart” file (107). The OS thenstores the DQuickStart file at a storage location from which it can beretrieved when needed, preferably on nonvolatile storage media such asdisk storage 34. When the ultrasound system is restarted under severalof the conditions discussed below, the OS retrieves the DQuickStart fileand initializes the ultrasound system for operation in the predetermineddefault operating state.

When a conventional ultrasound system is turned off, it proceeds througha lengthy process of terminating operations and shutting down modulesand processors. When the power-down process is completed, generally theonly circuit which is active is the battery-supported chip whichmaintains the system clock and calendar. All other circuitry iscompletely turned off. FIG. 2a illustrates a power-down state of thepresent invention from which full operability of the ultrasound systemmay be resumed fairly rapidly. Unlike the conventional power-downsequence, key system circuits continue to be energized. In FIG. 2a theOFF button is actuated (201) and the ultrasound system queries theoperator as to whether the current ultrasound exam is to be continuedwhen the system is restarted (202). In this example the operatorresponds that the current examination is to be continued. Theapplication data for the current exam is saved to RAM (203) and the OSpowers down the ultrasound signal path (204). The OS also powers downthe ultrasound system's peripheral devices or puts them in a suspendstate, including the hard drive (HD) disk storage 34 (205). The registerand stack values (context) of the CPU are saved to RAM (206) and a flagis set instructing the CPU to use the saved values when it is restarted(207). The CPU is then clocked at a low clock speed (208) to conserveenergy.

The ultrasound system may be restarted from this state by following theprocess charted in FIG. 3a. When the ultrasound system ON button isactuated (301) the CPU is clocked at its normal clock rate (302). Theperipheral devices including the hard drive are turned on (303) andpower is restored to the ultrasound signal path (304). The OS checks therestart flag (305) and finds that it is set to restart from RAM. Theregister and stack values of the CPU are restored from RAM (306) andchecked for corrupted data (307). Since the ultrasound system may havebeen left in its inactive state for a considerable period of time, suchas overnight or for several days or longer, it is prudent to check fordata corruption since the ultrasound system is being relied upon toprovide patient diagnostic information. If corrupted data is found, afull recovery bootup is performed (308). If no data corruption is foundthe data previously stored for the examination, the application data,and the scanhead data are restored to the ultrasound signal path (315).The system is now ready to continue the same exam that was underway whenit was turned off.

In this and the other quick start sequences described below, it is seenthat the step (104) of testing full functionality of the ultrasoundsignal path is not performed during the rapid restoration of systemoperability. That is because such self-testing can be verytime-consuming, detracting from the desired quick system restart.However, such functionality testing should be performed to continuallyassure accurate system functionality. In an embodiment of the presentinvention such functionality testing is performed at run-time, either aspart of mode transitions, in the background, or when periodic idle orpartially inactive states are encountered such as when an image isfrozen on the screen. Uninterrupted full functionality testing of theultrasound signal path is performed automatically on a cold startreboot. At other times such functionality testing is intermittentlyconducted by the OS when such scheduling can be conducted withoutinterruption of operations commanded by the operator, such as during thenight when the system is not in use. Thus, safety hazards and riskconcerns are abated on a periodic but continual basis.

Variations of these processes are possible. Instead of powering down theentire ultrasound signal path (204) the OS may leave some or all of theprocessors of the ultrasound signal path in one or more idle states orlow clock speeds, or turn off some of the components and modules of theultrasound signal path processors while leaving others energized. Forinstance, the volatile memory holding data for the beamformer may beleft in an energized condition. The OS can do this by commanding thesignal path power supply 18 by way of the control module 15 and thecommand line 17 to switch power off to all elements of the ultrasoundsignal path except the beamformer RAM. As another alternative, ratherthan switching the CPU to a low clock speed, the OS may issue a commandto the CPU power supply 32 over command line 36 to switch power off toall CPU board components except the board's RAM. While this action wouldincrease the time required by the system to return to full operability,it would enable the CPU power supply to operate at an output level ofapproximately 5 watts or less, which may be sustained by battery powerfor an appreciable amount of time.

FIG. 2b illustrates a procedure by which the ultrasound system is“turned off” to a lower state of readiness, requiring more time to berestored to full operability but exhibiting lower power consumption when“turned off.” After the operator actuates the OFF button (201) andelects to continue the current examination when the system is restarted(202), the application data for the current exam is save to RAM (203),the ultrasound signal path is powered down (204), the peripheral devicesare powered down (211), and the register and stack values of the CPU aresaved to RAM (206). The data stored in RAM is saved to nonvolatile diskor semiconductor storage (209) and a flag is set to notify the CPU tostart from the data in nonvolatile storage when operation is resumed.The disk drive and RAM is powered down and the CPU is 'switched to a lowclock speed. Alternatively, the CPU may also be powered down as the dataneeded on restart is retained in nonvolatile storage. This will requirethe CPU to reboot on restart, but will not require power to bemaintained to the CPU while the system is off.

The ultrasound system may be restarted from this off state by followingthe sequence shown in FIG. 3b. When the ON button is actuated (301) theprocess follows the same procedure diagramed in FIG. 3a up to the pointwhere the restart flag is checked (305). Here the OS sees that the“Start From Disk” flag has been set, and consequently the data stored onthe hard drive is restored to RAM (316). The register and stack valuesof the CPU are restored (306), and a data corruption check is performed(307). If no data corruption is found the examination application dataand the scanhead data are restored (315), and the system is once againready to continue the previous exam. As before, variations are possiblesuch as leaving portions of the ultrasound signal path energized and/oroperating at selected idle levels to enable a quicker restart.

In the previous scenarios the operator has elected to have the systemcontinue the current ultrasound exam when the ultrasound system isrestarted. FIG. 2c shows one possible scenario when the operator haselected not to continue the same exam on restart. When the operatormakes this election (202, the system queries whether the same type ofexamination as the most recent one is to be used on restart (212). Ifthe operator routinely uses the ultrasound system for a particular typeof cardiac exam, for instance, the choice might be made to restart thesystem for the same type of cardiac exam as that which has just beencompleted. But if the operator wants a different exam the next time thesystem is used or is not sure what type of exam will be performed nextby the system, the operator answers “No”, as shown in the drawing. TheOS responds by setting a flag for the DQuickStart file (213), poweringdown the ultrasound signal path (204), powering down the peripheralsincluding the hard drive (205), and setting the CPU to a low clock speed(208). When the system is restarted the ultrasound system follows thesequence shown in FIG. 3c. When the ON button is actuated (301) the CPUis returned to its normal clock speed (302) and the hard drive andperipheral devices are turned on (303). The ultrasound signal path isturned on (304) and the OS checks the restart flag (305). Upon findingthe DQuickStart flag set, the DQuickStart file is selected fromnonvolatile storage (309) and the previously set default operatingparameters are implemented. The ultrasound signal path is conditionedfor starting the default exam application (310) and the beamformer isset up to operate the default scanhead (311) or, if it is unavailable, ascanhead presently connected to the ultrasound system. The ultrasoundsystem is now ready to perform the default exam.

As in the previous examples, variations of this scenario may beemployed. Instead of switching the CPU to a low clock speed, the CPUboard can be turned off, as the DQuickStart file is stored innonvolatile storage; only the restart flag needs to be maintained. Thiswould take more time to restart, as the CPU board would have to berebooted. As another alternative which would result in an even fasterrestart, instead of setting the DQuickStart flag during the power-downsequence, the parameters of the DQuickStart file could be loaded intoRAM and power to the RAM maintained so that the OS could immediatelyimplement the DQuickStart application without having to recall theDQuickStart file from storage upon restart.

FIG. 2d shows a sequence of events that occur when the operator electsto begin the same type of exam as that which was just completed when theultrasound system is restarted. When the operator makes this election(212), the OS builds a file called CQuickStart, which containsparameters of the type of exam just completed, including the scanheadused (214). The CQuickStart file is saved to disk (or, in one of thealternatives described above, is stored in RAM), and a flag is set forthe CQuickStart file (215). The ultrasound signal path is powered down(204), the peripherals and hard drive powered down (205), and the CPU isset to a low clock speed (208). When the ultrasound system is turned on(301) as illustrated in FIG. 3d, the normal CPU clock speed is resumed(302), the hard drive and peripherals turned on (303), and theultrasound signal path is turned on (304). The OS checks the restartflag and finds that the CQuickStart flag is set (305). The OS retrievesthe CQuickStart file from disk (or implements it immediately if it wasstored in RAM) (312), and starts the exam application identified by theCQuickStart file (313), including setting up the beamformer for thescanhead identified by the file (314). The alternatives applicable tothe previous scenario of FIGS. 2c and 3 c are also applicable to thisone.

As mentioned above, when the OS powers down different elements of theultrasound system it will power them to an idle level which allows themto be returned to full operability in the timeframe required by theuser. Different elements of the ultrasound system may be set todifferent idle levels, and these levels may vary for different users asdifferent users may have different demands for the time in which theultrasound system must restart. The OS will also power down differentelements of the system in consideration of the type of functions theyperform, as previously illustrated by the example of maintaining powerto the beamformer memory. FIG. 4 illustrates another example of this. Anultrasound system which is externally accessible over a network or modemmay need to be available for remote querying at any time. For example,remote diagnostics may be performed at night when the ultrasound systemis not otherwise in use, as described for instance in U.S. patent[application Ser. No. 09/534,143, filed Mar. 23/00]. As another example,the diagnosing physician may want to review images stored on theultrasound system from his home after the ultrasound lab has closed forthe day. Such a scenario is described in U.S. Pat. No. 5,851,186. Inthese cases, the ultrasound system is essentially “on call” 24 hours aday. In this mode, when the ultrasound system is turned off at the endof the day, the network interface or modem may be in a suspend orpower-down state, but still aware of network or phone activity such thatit can be fully active if called. The CPU can be put in a low powerstate, or even turned off, so long as it continues to be responsive toan interrupt from the network or modem to handle external queries. TheCPU itself can be responsive to such an interrupt in an idle (e.g., lowclock speed) state, or the chipset on the CPU board can be responsive tosuch an interrupt and restart the CPU accordingly. In some cases theBIOS software on the CPU board can be programmed to handle theseinterrupts.

As an example, a physician desires to use his home computer to view animage acquired the previous business day by the ultrasound system. Thephysician connects to the ultrasound system either through the networkconnection or modem as shown in FIG. 4, which sends an interrupt to theCPU board (401). In the case where the CPU was powered down to a lowclock speed, the CPU responds to the interrupt by resuming its normalclock speed (402). In the case where the CPU was turned off, the CPUboard chipset responds to the interrupt by restarting the CPU. The harddrive and other peripherals may be turned on (403) if needed to respondto the request, as they may be required to run Web applications torespond to an Internet browser. The OS turns on the memory device wherethe ultrasound images are stored (404). In the example of FIG. 1 theultrasound images are stored on an image store 22 connected to theultrasound signal path and the CPU board. The OS then runs thecommunications software needed to respond to the request, such as Webapplications software (405). As described in the aforementioned patent,a Web server can transmit an image file index to the physician whoselects the image desired. The desired image is then retrieved from theimage memory or disk and transmitted over the network, modem, orInternet to the physician, who then views it on the screen of his homecomputer. After the communication has ended, the hard drive, imagememory, peripherals and CPU can be powered down again to await the nextquery in a low power state.

With the ultrasound system having the ability to power up and power downthe system selectively, a procedure such as that shown in FIG. 5 can beemployed to automatically restart the ultrasound system at apredetermined time. This allows the ultrasound system to be shut downwhen it is not used overnight, but to be ready for scanning when theultrasound lab is opened the next day. At the time the ultrasound systemis turned off, the operator enters a command for the ultrasound systemto restart at a designated time and date. If the ultrasound lab opens at8 a.m. the next day, it may be desirable to have the ultrasound systemturn on at 7:45 a.m. and to perform a self-diagnosis at the time so thatthe system is fully ready for scanning at 8 a.m. When the operator turnsthe ultrasound system off, the selection is made to restart the systemfor the default exam or a custom exam (including the most recentlyperformed exam as explained above), and the appropriate QuickStart fileis flagged. The system is then shut down to the desired idle level; inthis example, the CPU is switched to a low clock speed. A timer in theultrasound system, which may be implemented on the CPU board, keepstrack of the time and when the appointed start time occurs the timersends an interrupt to the CPU board (501). In response to the interruptthe CPU returns to the normal clock speed (502), and the OS turns on thehard drive and peripherals (503). The OS then checks to see whether thea flag is set for the default exam or a custom exam (504). If thedefault exam has been flagged, the ultrasound signal path is turned on(505) and the DQuickStart file is retrieved. The beamformer isprogrammed for the scanhead used in the default examination (508) andthe default exam application is set up on the ultrasound system (510). Afull self-test of system functionality may be performed. The ultrasoundsystem is then fully ready for scanning when the operator arrives to useit.

When the OS finds that the custom exam flag has been set, the ultrasoundsignal path is turned on (505) and the CQuickStart file is retrieved(507) which contains the parameters of the exam which the operator wantsto perform first. The beamformer is programmed for the scanhead of thecustom exam (509) and the custom exam application is set up on theultrasound system (511). A full self-test of system functionality may beperformed. Thus, the ultrasound system is ready to use immediately whenthe ultrasound lab is opened in the morning without having to leave thesystem fully powered up overnight.

As discussed above, a high performance ultrasound system can consumeapproximately 1000 watts of power, even when sitting unused. This powerconsumption will produce a heating effect which must be dissipated bythe lab or hospital's air conditioning system, which costs money.Furthermore, the heating of components in the system can reducecomponent life, leading to degraded system reliability. FIG. 6illustrates an approach to reducing this cost and unnecessary componentheat dissipation, which is for the ultrasound system to progressivelyturn off its modules and subsystems when it is sitting unused for aperiod of time. In a preferred implementation the user is given theopportunity to activate or deactivate such a progressive shutdown,select the time which passes before the progressive shutdown commences,and select the time passages between the successive steps of theshutdown. The order in which the various components of the system shutdown can also be changed. In the progressive sequence of FIG. 6 thefirst element to be shut down is the display device, which may first beput on standby (601) and, after a further passage of time, completelypowered down. After further time the OS powers down the ultrasoundsystem peripheral devices such as printers and recorders (602). Afterfurther time, any unsaved exam data and the register and stack values ofthe CPU (context) are stored to RAM (603) and the RAM data saved to disk(604). The ultrasound signal path is powered down (605) and the CPUboard's peripherals and hard drive are powered down (606). Finally theCPU is set to an idle state, in this example a low clock speed (607).The ultrasound system is now consuming only a small amount of power,perhaps 5 watts or less, but the CPU, still being energized, can restartthe ultrasound system in a relatively short amount of time.

In a variation of the sequence of FIG. 6, the OS is continuallymonitoring the use of the ultrasound system and turning modules andcomponents off and on where the situation permits to effect a loweroverall power consumption and component heating. Modules and subsystemsmay be placed into low power states for seconds and even fractions ofseconds where possible to achieve this. For example, the operator mayinterrupt real time imaging to freeze an image on the display screen.Sensing this state, the OS can maintain power to the display 16, theimage store 22 where the frozen image is stored, and that portion of theultrasound signal path which applies image display signals to thedisplay such as the video driver of the system. The transmit and receivebeamformers can be set to an inactive, low power state at this time, ascan the signal and image processing portions of the ultrasound signalpath 14, since real time imaging has been suspended. To the operator,this suspend state is transparent, as the frozen image is maintained onthe display as the operator has commanded. This reduces the powerconsumption and heating of those subsystems of the ultrasound signalpath 14 which have been placed in the low power state. The 1200 wattconsumption of an ultrasound signal path can be momentarily reduced to200 watts, for example. When the operator unfreezes the image to resumereal time imaging, the low power subsystems are restored to fulloperability immediately, without any interruption in system operabilityapparent to the operator. Over time, such periodic reductions in powerconsumption can reduce the heating and hence prolong the life ofcomponents of the ultrasound signal path, as well as reduce the airconditioning load imposed by the ultrasound system.

While such periodic reductions in system power consumption will reducethermal emission by the ultrasound system, this capability may also beused to reduce audible emission as well. The noise made by an operatingultrasound system is the humming of fans used to cool the electroniccomponents and power supplies. When the overall power consumption of theultrasound system and component heating are reduced, the need for fancooling is reduced as well. When individual components, modules, orsubsystems are powered down or turned off even for short intervals, thefans used to cool them can be operated at a reduced fan speed or evenperiodically turned off. Thus, thermal levels in the ultrasound systemcan be monitored by the CPU board OS and the speed of the cooling fansadjusted when possible. It may be appreciated that during a 30 minuteultrasound exam, the system operator may spend half the time changingoperating states, making measurements on frozen images, talking to thepatient, and other non-real-time scanning activities. Advantage can betaken of these circumstances by the OS to control the ultrasound systemso that it is fully operational only when required. This can lead to areduction in thermal and noise pollution by an equivalent amount.

The embodiment of FIG. 1 is seen to include a battery backup, an interimpower source which can sustain key elements of the ultrasound system forperiods when a.c. power is not available. This ability to sustain keyelements such as the CPU and RAM even when the system is not plugged into its a.c. power source enables the ultrasound system to be moved andrestarted very quickly to meet the needs of a modern hospital. Asexplained at the outset of this patent, it is often necessary to quicklymove an ultrasound system from one area of a hospital to another toperform a diagnosis in another department of the hospital as soon aspossible. But this cannot be done when an ultrasound system has tosequence through a lengthy shutdown procedure before it can be turnedoff and unplugged, and must go through a lengthy boot-up sequence whenrestarted at the new location. The ultrasound system shown in FIG. 1 byuse of the processes shown in the preceding flowcharts can be quicklymoved without these delays. For example suppose that the ultrasoundsystem is called to be moved from the ultrasound lab to the deliveryroom in obstetrics for an immediate scan. The operator can touch the OFFbutton, pull the ultrasound system plug 40 from the wall, and begin tomove the ultrasound system to the obstetrics ward without waiting forany of the shutdown procedure to occur. When the plug is pulled theultrasound system switches to its backup battery power source, and as itis being moved the ultrasound system will shut itself down using one ofthe sequences described above. The ultrasound system can shut itselfdown for a restart to the default exam (which may in this example be anobstetrical exam) or to the most recently used exam for instance.Preferably the ultrasound system under these conditions will not shutthe CPU down completely, but will leave the CPU and its RAM energized sothat the system can be restarted quickly when it arrives at theobstetrics ward for the emergency exam. If desired, the OS can beprogrammed to respond to a loss of a.c. power during a shutdown sequenceby powering down to a high state of readiness from which it can bereturned to full operability almost instantly. For example, by sensingthe loss of a.c. power, or sensing the switchover to battery power, ordetecting the lack of operator responses to the queries posed duringshutdown (e.g., restart the same exam?) the OS would continue tomaintain power to all processors and volatile storage devices (RAM) inthe ultrasound system for as long as sufficient battery power wasavailable to do so. As another example the ultrasound system mayexperience an inadvertent loss of a.c. power, for instance, if the a.c.power cord is accidentally pulled from the wall or the circuit breakerfor the a.c. line powering the system trips. In such instances the OSautomatically performs a shutdown such that the current exam is resumedon restart (FIGS. 2a and 3 a). Alternatively, if battery capacity issufficient, the ultrasound system can be powered in a fully active stateby the battery until the battery is substantially discharged, at whichpoint a shutdown is automatically performed. Devices which consumerelatively large amounts of energy and do not retain critical data involatile storage, such as the display and the scanhead's transducerdrivers, could be shut down to conserve battery power while stillaffording the ability to restart almost instantly. When the ultrasoundsystem arrives in the obstetrics ward in the first example, is pluggedin, and the ON button depressed, it is ready for scanning virtuallyimmediately.

In an embodiment where the ultrasound system does not contain batterybackup power, some of the aforementioned delays can still be avoided.For instance, sufficiently sized capacitors in the power supply systemcan retain sufficient energy to sustain an OS shutdown sequence even inthe absence of battery backup. Such capacitively stored energy couldpower the CPU board for the time required to complete an orderlyshutdown. The operator could thus press the OFF button, pull the a.c.plug from the wall and begin to move the ultrasound system. Thecapacitive source would provide power for shutdown during this time.When the CPU board senses that a.c. power has been lost prior tocompletion of a normal shutdown, the OS can immediately cut power fromnonessential or high power consuming devices such as the display,transducer drivers, printers and recorders. The capacitively storedpower would then be sustainable to shut down data components andprocessors in a rapid but orderly manner. This shutdown sequence wouldend with the complete shutdown of all components in the ultrasoundsystem, including the CPU and RAM on the CPU board.

What is claimed is:
 1. An ultrasound system with rapid startupcapability comprising: an ultrasound signal path; a processor, coupledto the ultrasound signal path and responsive to an operator controlledsystem ON or OFF signal; and control software running on the processorwhich controls the state of the ultrasound signal path, wherein thecontrol software runs when the ultrasound signal path is turned off, andwherein the control software is running prior to actuation of the systemON signal by a system operator, and is responsive to the system ONsignal to turn the ultrasound signal path on.
 2. The ultrasound systemof claim 1, wherein the control software comprises operating systemsoftware.
 3. The ultrasound system of claim 1, wherein the controlsoftware comprises application software.
 4. A method for powering-downan ultrasound system comprising: turning off at least a portion-of anultrasound signal path in response to a user command; and maintainingpower to a processor which is responsive to a user command to restorethe ultrasound signal path to an operational state.
 5. The method ofclaim 4, wherein maintaining further comprises maintaining theoperability of operating system software on the processor.
 6. The methodof claim 4, wherein maintaining further comprises maintaining theoperability of application software on the processor.
 7. The method ofclaim 4, further comprising storing context information.
 8. The methodof claim 7, wherein storing comprises storing context information involatile memory.
 9. The method of claim 8, further comprisingmaintaining power to the volatile memory when the ultrasound signal pathis turned off.
 10. The method of claim 7, wherein storing comprisesstoring context information in nonvolatile memory.
 11. The method ofclaim 10, further comprising switching the nonvolatile memory to asuspend state.
 12. The method of claim 11, wherein the suspend statecomprises a powered-down state.
 13. A method for powering down andrestarting an ultrasound system comprising: responding to an operatorcommand to turn off the system by: a) turning off at least a portion ofan ultrasound signal path; b) storing context data in a volatile memory;and c) maintaining power to the volatile memory while at least a portionof the ultrasound signal path is turned off; and responding to anoperator command to turn on the system by: d) restoring system operationby use of the context data; and e) restoring the ultrasound signal pathto an operational state.
 14. The method of claim 13, wherein storingcomprises storing context data of a processor in the volatile memory;and wherein restoring comprises using the context data to reset theoperating state of the processor.
 15. A method for powering down andrestarting an ultrasound system comprising: responding to an operatorcommand to turn off the system by: a) turning off at least a portion ofan ultrasound signal path; b) storing system context data in anonvolatile storage device; and responding to an operator command toturn on the system by: c) accessing the system context data stored inthe nonvolatile storage device; and d) restoring the ultrasound signalpath to an operational state.
 16. The method of claim 15, furthercomprising using the system context data stored in the nonvolatilestorage device to reset the operating state of a processor.
 17. Themethod of claim 15, wherein the ultrasound system includes a processoroperatively associated with a volatile memory and the nonvolatilestorage device; and wherein the processor acts to store context data ofthe volatile memory in the nonvolatile memory.
 18. The method of claim17, wherein the processor and volatile memory are powered down after thecontext data is stored in the nonvolatile memory.
 19. The method ofclaim 15, further comprising: setting the nonvolatile storage device toa suspend state after storing system context data; and resetting thenonvolatile storage device to an active state in response to the commandto turn on the system.
 20. A method for turning off an ultrasound systemcomprising: turning off at least a portion of an ultrasound signal pathin response to a user command; reducing the clock speed of a processor;and maintaining power to a volatile memory coupled to the processor. 21.A method for powering down and restarting an ultrasound systemcomprising: responding to an operator command to turn off the system by:a) turning off at least a portion of an ultrasound signal path; b)reducing the clock speed of a processor; and c)maintaining power to avolatile memory coupled to the processor; and responding to an operatorcommand to turn on the system by: e) increasing the clock speed of theprocessor; and f) restoring the ultrasound signal path to an operationalstate.
 22. An ultrasound system with rapid startup comprising: anultrasound signal path; a processor, coupled to the ultrasound signalpath and responsive to an operator controlled system ON or OFF signal;and an operating system running on the processor which controls thestate of the ultrasound signal path, wherein the operating systemoperates while the ultrasound signal path is turned off, and wherein theoperating system operates prior to actuation of the system ON signal bya system operator, and is responsive to the system ON signal to turn theultrasound signal path on.
 23. A method for powering down an ultrasoundsystem comprising: turning off at least a portion of an ultrasoundsignal path in response to a user command; and maintaining power to avolatile memory which retains system context data while at least aportion of the ultrasound signal path is turned off.
 24. A method forpowering down an ultrasound system having an ultrasound signal path anda volatile storage device connected thereto which stores data used bythe ultrasound signal path comprising: turning off at least a portion ofthe ultrasound signal path in response to a user command; andmaintaining power to the volatile storage device to retain the datatherein for use when the ultrasound signal path is turned on.
 25. Themethod of claim 24, wherein the ultrasound signal path includes abeamformer, wherein the volatile storage device stores beamformer data,and wherein maintaining comprises maintaining power to the volatilestorage device to retain beamformer data for subsequent use by thebeamformer.